JP4624423B2 - Receiver - Google Patents

Abstract

A timing synchronization detects a temporary timing in a manner such that the presence of a first known signal in the received packet signal is detected by performing correlation processing on the first known signal in the received packet signal. The timing synchronization detects a timing in a manner that when the presence of a second known signal is detected, correlation processing is performed on the second known signal in the received packet signal. In the timing synchronization unit, a correlator is commonly used to perform two correlation processings.

Description

  The present invention relates to a reception technique, and more particularly, to a reception method and apparatus for detecting timing with respect to a received packet signal, and a communication system using the reception method and apparatus.

  An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. This OFDM modulation scheme is applied to IEEE802.11a, g and HIPERLAN / 2, which are standardization standards for wireless LAN (Local Area Network). A packet signal in such a wireless LAN is generally transmitted via a transmission path environment that fluctuates with time, and is affected by frequency selective fading. Therefore, a receiving apparatus generally performs transmission path estimation dynamically. Execute.

In order for the receiving apparatus to perform transmission path estimation, two types of known signals are provided in the packet signal. One is a known signal provided for all carriers at the beginning of the packet signal, which is a so-called preamble or training signal. The other is a known signal provided for some of the carriers in the data interval of the packet signal, which is a so-called pilot signal (see, for example, Non-Patent Document 1).
Sine Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai, "Channel Estimation Techniques Based on Pilot Arrangement in OFDM Systems", IbnEstemEs. 48, no. 3, pp. 223-229, Sept. 2002.

  One technique for effectively using frequency resources in wireless communication is an adaptive array antenna technique. The adaptive array antenna technology controls the directivity pattern of an antenna by controlling the amplitude and phase of a signal to be processed in each of a plurality of antennas. There is a MIMO (Multiple Input Multiple Output) system as a technique for increasing the data rate by using such adaptive array antenna technology. In the MIMO system, each of a transmission apparatus and a reception apparatus includes a plurality of antennas and sets packet signals to be transmitted in parallel (hereinafter, each piece of data to be transmitted in parallel in the packet signal is referred to as a “sequence”). . That is, the data rate is improved by setting a sequence up to the maximum number of antennas for communication between the transmission device and the reception device.

  Furthermore, when such an MIMO system is combined with an OFDM modulation scheme, the data rate is further increased. A known signal defined in a communication system that is not a MIMO system (hereinafter referred to as “conventional system”) is arranged at the beginning of a packet signal in such a MIMO system. Therefore, the receiving apparatus of the conventional system can recognize the head part of the packet signal and recognize that it is a packet signal that should not be received by itself. As a result, the receiving apparatus of the conventional system stops the reception of the remaining part of the packet signal, so that power consumption can be reduced. Also, in the packet signal in the MIMO system, a known signal defined in the MIMO system is also arranged behind the known signal in the conventional system. This is because the MIMO system transmits a plurality of sequences and the conventional system transmits one sequence, so that the signal strength in the receiving device is different, and the receiving device sets the gain of the amplifier accordingly. It is.

  In addition, the receiving apparatus executes timing detection, frequency offset detection, reception weight vector derivation, transmission path estimation, and the like based on the known signal. Here, the detection of timing is the subject of explanation. When receiving the packet signal, the receiving device detects the presence of the packet signal and also detects the timing. Therefore, the receiving apparatus performs correlation processing between the received packet signal and the conventional known signal, and detects the peak of the correlation value. At that time, in order to improve the detection accuracy of the presence of the packet signal, a packet signal having a long delay time should be received, and the range in which the addition is performed in the correlation processing (hereinafter referred to as “correlation window”) should be widened. It is. However, when the correlation window is widened, a timing at which a plurality of delayed wave components included in the received packet signal are combined is detected. Therefore, timings that take into account the effects of the components of the plurality of delayed waves included in the received packet signal are not detected. As a result, highly accurate timing detection cannot be performed.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a reception technique for detecting timing while taking into account a component of a delayed wave.

  In order to solve the above-described problem, in a receiving device according to an aspect of the present invention, a first data signal is arranged after the first known signal, and a second known signal is arranged after the first data signal. A reception unit that receives the packet signal in which the second data signal is arranged in the subsequent stage of the second known signal, and performs correlation processing on the first known signal among the packet signals received by the reception unit The first detector that detects the provisional timing while detecting the presence of the first known signal in the packet signal, and the first data in the packet signal at the provisional timing detected by the first detector A first processing unit that detects the presence of a second known signal in the packet signal by processing the signal, and a reception unit that receives the second known signal when the first processing unit detects the presence of the second known signal Pake A second detection unit for detecting timing and processing a second data signal in the packet signal at the timing detected by the second detection unit And a second processing unit. The width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit.

  The “correlation process with respect to the first known signal in the received packet signal” indicates a correlation process executed to detect the first known signal from the received packet signal. For this reason, in the correlation processing, the object whose correlation is calculated with the received packet signal may be arbitrary, and the correlation value becomes large at the timing when the first known signal in the received packet signal is arranged. Any signal may be used. The same applies to “correlation processing for the second known signal in the received packet signal”.

  According to this aspect, the width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit. The first known signal can be detected with high probability in the unit, and the timing can be detected with high accuracy in the second detection unit.

  Another embodiment of the present invention is also a receiving device. In this apparatus, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data is arranged after the second known signal. The presence of the first known signal in the packet signal is detected by executing a correlation process between the receiving unit that receives the packet signal in which the signal is arranged and the received packet signal and the first known signal in the receiving unit. However, the first detection unit that detects the tentative timing and the second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit. When the presence of the second known signal is detected by the first processing unit that detects the presence of the signal and the first processing unit, correlation processing between the received packet signal and the second known signal is executed by the receiving unit. By Te, comprising a second detector for detecting a timing and a second processing unit for processing the second data signal in the packet signal at a timing detected in the second detector. The width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit.

  According to this aspect, the width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit. The presence of the first known signal can be detected with high probability in the unit, and the timing can be detected with high accuracy in the second detection unit.

  You may share the correlator for performing a correlation process in a 1st detection part, and the correlator for performing a correlation process in a 2nd detection part. In this case, since the correlator to be used for the two correlation processes is shared, an increase in circuit scale can be reduced.

  Yet another embodiment of the present invention is also a receiving device. In this apparatus, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data is arranged after the second known signal. A receiving unit that receives the packet signal in which the signal is arranged, and performing autocorrelation processing on the packet signal received by the receiving unit, while detecting the presence of the first known signal in the packet signal; The presence of the second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected in the first detection unit. When the presence of the second known signal is detected by the first processing unit to be detected and the first processing unit, by performing a cross-correlation process between the packet signal received by the receiving unit and the second known signal Comprising a second detector for detecting a timing and a second processing unit for processing the second data signal in the packet signal at a timing detected in the second detector. The window width when the cross-correlation process is executed in the second detection unit is set to be narrower than the window width when the auto-correlation process is executed in the first detection unit.

  According to this aspect, the width of the window when the cross-correlation process is performed in the second detection unit is set to be narrower than the width of the window when the auto-correlation process is performed in the first detection unit. The presence of the first known signal can be detected with high probability in one detection unit, and the timing can be detected with high accuracy in the second detection unit. In addition, since the autocorrelation process and the cross correlation process are used, both the detection accuracy of the presence of the first known signal and the detection accuracy of the timing can be improved.

  The receiving unit also receives another packet signal including the first known signal. In the other packet signal, the arrangement of the signal points in the latter part of the first known signal is the first data. The first processing unit is different from the signal point arrangement in at least a part of the signal, and the signal processing point arrangement in the latter part of the first known signal among the packet signals received by the receiving unit is the first. The presence of the second known signal in the packet signal may be detected as long as it corresponds to the arrangement of signal points in at least a part of the data signal. In this case, since the presence of the second known signal is detected according to the arrangement of the signal points, an additional signal for notifying the presence can be eliminated, and deterioration in transmission efficiency can be prevented.

  The packet signal received by the receiving unit is composed of a plurality of sequences, and a second known signal arranged in another sequence on the basis of the second known signal arranged in one of the plurality of sequences. Includes a cyclic timing shift within the second known signal, and the second detection unit, based on the correlation value, performs a timing shift corresponding to the timing corresponding to the second known signal serving as a reference. The timing corresponding to the second known signal for which the timing shift has been made among the timing candidates derived in the derivation unit On the other hand, a moving unit that performs movement of timing according to the amount of timing shift, timing moved by the moving unit, and timing derived by the deriving unit Based on the timing corresponding to the second known signal as a reference of the candidate A, and a determination unit for determining a timing. In this case, since one timing is determined from the timing corresponding to each of the plurality of sequences, the influence of each of the plurality of sequences can be taken into account, and the timing can be detected with high accuracy.

  The determination unit may select a timing that exists ahead of the timing moved by the moving unit and the timing corresponding to the second known signal that is the reference among the timing candidates derived by the deriving unit. Good. In this case, since the timing existing ahead is selected from a plurality of timings, interference with a signal arranged behind can be reduced, and reception characteristics can be improved.

  You may further provide the memory | storage part which memorize | stores the packet signal received in the receiving part. When the second processing unit processes the second data signal in the packet signal at the timing detected by the second detection unit, the second processing unit also processes the first data signal in the packet signal stored in the storage unit again. Also good. In this case, since the first data signal is processed again at the timing detected with high accuracy, the processing accuracy of the first data signal can be improved.

  Yet another embodiment of the present invention is a communication system. In this communication system, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second known signal is arranged after the second known signal. A transmission device that transmits a packet signal in which a data signal is arranged, and a reception device that receives a packet signal from the transmission device. The receiving device performs a correlation process on the first known signal in the received packet signal, thereby detecting the provisional timing while detecting the presence of the first known signal in the packet signal. A first processing unit that detects the presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit; A second detection unit that detects timing by executing a correlation process on the second known signal in the received packet signal when the first processing unit detects the presence of the second known signal; And a second processing unit that processes the second data signal in the packet signal at the timing detected by the two detection units. The width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit.

  According to this aspect, the width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit. The presence of the first known signal can be detected with high probability in the unit, and the timing can be detected with high accuracy in the second detection unit.

  Yet another embodiment of the present invention is a reception method. In this method, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data is arranged after the second known signal. Detecting the presence of the first known signal in the packet signal by performing a correlation process on the first known signal of the received packet signal, and receiving the packet signal in which the signal is arranged; Detecting a provisional timing; detecting a presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the detected provisional timing; Detecting the timing by performing correlation processing on the second known signal of the received packet signals, and detecting the presence of the known signal And a step of processing the second data signal in the packet signal at timing. The window width when executing the correlation process in the step of detecting timing is set to be narrower than the window width when executing the correlation process in the step of detecting temporary timing.

  Yet another embodiment of the present invention is also a reception method. In this method, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data is arranged after the second known signal. While detecting the presence of the first known signal in the packet signal by performing a step of receiving the packet signal in which the signal is arranged and performing correlation processing between the received packet signal and the first known signal, Detecting the presence of the second known signal in the packet signal by processing the first data signal in the packet signal at the detected tentative timing, When the presence of the known signal is detected, a correlation process between the received packet signal and the second known signal is performed to detect the timing, and the packet is detected at the detected timing. And a step of processing the second data signal in the signal. The window width when executing the correlation process in the step of detecting timing is set to be narrower than the window width when executing the correlation process in the step of detecting temporary timing.

  You may share the correlator for performing a correlation process in the step which detects temporary timing, and the correlator for performing a correlation process in the step which detects a timing.

  Yet another embodiment of the present invention is also a reception method. In this method, the first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data is arranged after the second known signal. Detecting provisional timing while detecting the presence of the first known signal in the packet signal by receiving the packet signal in which the signal is arranged and performing autocorrelation processing on the received packet signal Detecting the presence of the second known signal in the packet signal by processing the first data signal in the packet signal at the detected tentative timing; and the presence of the second known signal Is detected, the cross-correlation process between the received packet signal and the second known signal is executed to detect the timing, and the packet signal is detected at the detected timing. And a step of processing the second data signal in. The width of the window when executing the cross-correlation process in the step of detecting timing is set to be narrower than the width of the window when executing the auto-correlation process in the step of detecting temporary timing.

In the receiving step, another packet signal including the first known signal is also received, and in the other packet signal, the arrangement of signal points in the subsequent stage of the first known signal is the first Different from the arrangement of signal points in at least part of the data signal,
In the step of detecting the presence of the second known signal in the packet signal, the arrangement of the signal points in the subsequent portion of the first known signal in the received packet signal is at least part of the first data signal. The presence of the second known signal in the packet signal may be detected as long as it corresponds to the arrangement of the signal points.

  The packet signal received in the receiving step is composed of a plurality of sequences, and a second known signal arranged in another sequence based on a second known signal arranged in one of the plurality of sequences. The signal is subjected to a cyclic timing shift within the second known signal, and the step of detecting the timing is based on the correlation value and the timing corresponding to the second known signal serving as a reference. A step of deriving a timing corresponding to the second known signal subjected to the timing shift as a timing candidate, and a timing corresponding to the second known signal subjected to the timing shift among the derived timing candidates , A step of performing a timing shift according to the timing shift amount, a timing of the shift, and a candidate of the derived timing. And a timing corresponding to a known signal based on a second of the criteria may include the step of determining a timing.

  In the step of determining the timing, a timing existing ahead may be selected from the moved timing and the timing corresponding to the second known signal serving as a reference among the derived timing candidates. The step of storing the received packet signal in a memory is further included, and the step of processing the second data signal in the packet signal is performed when the second data signal in the packet signal is processed at the detected timing. The first data signal in the stored packet signal may be processed again.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, the timing can be detected while taking into account the delayed wave component.

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 3A and 3B are diagrams showing packet formats in the communication system of FIG. It is a figure which shows the structure of the 1st radio | wireless apparatus of FIG. It is a figure which shows the structure of the signal of the frequency domain in FIG. 6 (a)-(b) is a diagram showing a constellation of L-SIG and HT-SIG in FIGS. 3 (a)-(b). FIG. 5 is a diagram illustrating a configuration of a timing synchronization unit in FIG. 4. It is a figure which shows the format of L-STF in FIG. 3 (a)-(b), and HT-STF. It is a figure which shows the structure of the correlation part of FIG. FIGS. 10A and 10B are diagrams illustrating a delay profile of a signal input to the correlation unit in FIG. FIGS. 11A to 11D are diagrams illustrating an outline of timing determination in the determination unit of FIG. It is a figure which shows the structure of the baseband process part of FIG. It is a figure which shows the structure of the process part for reception of FIG. It is a figure which shows the structure of the process part for transmission of FIG. It is a flowchart which shows the procedure of the timing synchronization process in the timing synchronization part of FIG.

Explanation of symbols

  10 wireless devices, 12 antennas, 14 antennas, 20 wireless units, 22 baseband processing units, 24 modem units, 26 IF units, 30 control units, 32 timing synchronization units, 34 correlation units, 36 window setting units, 38 peak detection units , 40 determining unit, 42 moving unit, 44 comparing unit, 100 communication system.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a MIMO system composed of at least two wireless devices. One of the wireless devices corresponds to a transmitting device, and the other corresponds to a receiving device. Packet signals are used for communication in a MIMO system. A known signal (hereinafter referred to as “L-STF”) in the conventional system is arranged at the head portion of the packet signal. Further, a control signal (hereinafter referred to as “HT-SIG”) in the MIMO system is arranged subsequent to the L-STF, and a known signal (hereinafter referred to as “HT-STF” in the MIMO system is disposed subsequent to HT-SIG. Is arranged). Further, data is arranged at the subsequent stage of the HT-STF. The receiving apparatus performs a cross-correlation process between the received packet signal and the L-STF, detects the presence of the packet signal from the correlation value, and detects provisional timing. Here, in order to improve the detection accuracy of the presence of the packet signal, the window width at the time of cross-correlation processing is set to, for example, 800 nsec so as to increase to some extent.

  On the other hand, after HT-STF is defined by a plurality of sequences, and HT-STF arranged in a sequence other than one sequence (hereinafter referred to as “reference sequence”) is HT-STF arranged in the reference sequence. Is defined by a cyclically shifted timing pattern. Further, the timing shift amount is set to be different depending on the series, and is set to, for example, -400 nsec and -200 nsec. This is equivalent to the fact that HT-STF delay waves are formed in advance between a plurality of streams. The provisional timing described above corresponds to an average timing because it is detected while using a window width having a somewhat large value. Therefore, the timing is not derived while taking into account the influence of each delayed wave component. The receiving apparatus according to the present embodiment executes the following processing in order to derive the timing in consideration of the influence of each delayed wave component.

  The receiving apparatus detects the presence of the HT-STF by processing the HT-SIG at the tentative timing after the tentative timing is detected. In addition, the receiving apparatus executes a cross-correlation process between the received packet signal and the HT-STF while reducing the window width, for example, 400 nsec. As a result, the timing corresponding to the reference sequence and the timing at which the timing shift is made are derived from the correlation value. The receiving apparatus moves the latter timing backward by the timing shift amount. Further, the receiving apparatus compares the timing corresponding to the reference sequence with the moved timing, thereby selecting a timing positioned in front, and determining the selected timing as the timing of the packet signal.

  FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention. In particular, FIG. 1 shows the spectrum of a signal in the OFDM modulation scheme. One of a plurality of carriers in the OFDM modulation scheme is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. In the MIMO system, 56 subcarriers from subcarrier numbers “−28” to “28” are defined. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. On the other hand, in the conventional system, 52 subcarriers from subcarrier numbers “−26” to “26” are defined. An example of a conventional system is a wireless LAN compliant with the IEEE802.11a standard. Further, one signal unit composed of a plurality of subcarriers and one signal unit in the time domain is referred to as an “OFDM symbol”.

  Each subcarrier is modulated by a variably set modulation method. As the modulation method, any one of BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64 QAM is used.

  Also, convolutional coding is applied to these signals as an error correction method. The coding rate of convolutional coding is set to 1/2, 3/4, and the like. Furthermore, the number of data to be transmitted in parallel is set variably. Note that data is transmitted as packet signals, and each of the packet signals transmitted in parallel is called a “sequence” as described above. As a result, the data rate is also variably set by variably setting the modulation scheme, coding rate, and number of sequences. The “data rate” may be determined by any combination of these, or may be determined by one of them. In the conventional system, when the modulation method is BPSK and the coding rate is 1/2, the data rate is 6 Mbps. On the other hand, when the modulation method is BPSK and the coding rate is 3/4, the data rate is 9 Mbps.

  FIG. 2 shows a configuration of the communication system 100 according to the embodiment of the present invention. The communication system 100 includes a first wireless device 10a and a second wireless device 10b collectively referred to as a wireless device 10. The first radio apparatus 10a includes a first antenna 12a, a second antenna 12b, a third antenna 12c, and a fourth antenna 12d, which are collectively referred to as an antenna 12, and the second radio apparatus 10b is collectively referred to as an antenna 14. A first antenna 14a, a second antenna 14b, a third antenna 14c, and a fourth antenna 14d are included. Here, the first radio apparatus 10a corresponds to a transmission apparatus, and the second radio apparatus 10b corresponds to a reception apparatus.

  As a configuration of the communication system 100, an outline of a MIMO system will be described. It is assumed that data is transmitted from the first radio apparatus 10a to the second radio apparatus 10b. The first radio apparatus 10a transmits a plurality of series of data from each of the first antenna 12a to the fourth antenna 12d. As a result, the data rate is increased. The second radio apparatus 10b receives a plurality of series of data by the first antenna 14a to the fourth antenna 14d. Furthermore, the second radio apparatus 10b separates the received data by adaptive array signal processing and independently demodulates a plurality of series of data.

  Here, since the number of antennas 12 is “4” and the number of antennas 14 is also “4”, the combination of transmission paths between the antennas 12 and 14 is “16”. A transmission path characteristic between the i-th antenna 12i and the j-th antenna 14j is denoted by hij. In the figure, the transmission line characteristic between the first antenna 12a and the first antenna 14a is h11, the transmission line characteristic between the first antenna 12a and the second antenna 14b is h12, the second antenna 12b and the first antenna. 14a, the transmission path characteristic between the second antenna 12b and the second antenna 14b is h22, and the transmission path characteristic between the fourth antenna 12d and the fourth antenna 14d is h44. Has been. Note that transmission lines other than these are omitted for the sake of clarity. The first radio apparatus 10a and the second radio apparatus 10b may be reversed.

  3A to 3B show packet formats in the communication system 100. FIG. 3A corresponds to the packet format defined in the MIMO system, and FIG. 3B corresponds to the packet format defined in the conventional system. In FIG. 3A, it is assumed that data included in the four sequences is to be transmitted, and packet formats corresponding to the first to fourth sequences are shown in order from the top to the bottom. In the packet signal corresponding to the first stream, “L-STF”, “HT-LTF”, and the like are arranged as preamble signals. “L-STF”, “L-LTF”, “L-SIG”, “HT-SIG” are known signals for timing estimation, known signals for transmission path estimation, control signals, MIMO systems corresponding to conventional systems Correspond to the control signals corresponding to. The control signal corresponding to the MIMO system includes, for example, information regarding the number of sequences. “HT-STF” and “HT-LTF” correspond to a known signal for timing estimation and a known signal for channel estimation corresponding to the MIMO system. On the other hand, “data 1” is a data signal. Note that “L-STF” and “HT-STF” have the same pattern.

  Also, in the packet signal corresponding to the second stream, “L-STF (−50 ns)”, “HT-LTF (−400 ns)” and the like are arranged as preamble signals. Further, in the packet signal corresponding to the third stream, “L-STF (−100 ns)”, “HT-LTF (−200 ns)”, and the like are arranged as preamble signals. In the packet signal corresponding to the fourth stream, “L-STF (−150 ns)”, “HT-LTF (−600 ns)”, and the like are arranged as preamble signals. Here, “−400 ns” or the like indicates a shift amount in CDD (Cyclic Delay Diversity). CDD is a process in which a waveform in the time domain is shifted backward by a shift amount in a predetermined section, and a waveform pushed out from the last part of the predetermined section is cyclically arranged at the head portion of the predetermined section. That is, “L-STF (−50 ns)” is cyclically shifted with a delay amount of −50 ns with respect to “L-STF”.

  In the first stream, HT-LTFs are arranged in the order of “HT-LTF”, “−HT-LTF”, “HT-LFT”, and “−HT-LTF” from the top. Here, these are sequentially referred to as “first component”, “second component”, “third component”, and “fourth component” in all series. If the calculation of the first component-second component + third component-fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the first series. Further, if the calculation of the first component + second component + third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the second series. Further, if the calculation of the first component-second component-third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the third series. Also, if the calculation of the first component + second component−third component−fourth component is performed on the received signals of all sequences, the desired signal for the fourth sequence is extracted in the receiving apparatus. The addition / subtraction process is executed by vector calculation.

  The parts from “L-LTF” to “HT-SIG1” use “52” subcarriers as in the conventional system. Of the “52” subcarriers, “4” subcarriers correspond to pilot signals. On the other hand, “56” subcarriers are used in the subsequent parts such as “HT-LTF”. In FIG. 3B, “L-STF”, “L-LTF”, and “L-SIG” are arranged as in FIG. Furthermore, “data” is arranged after “L-SIG”.

  FIG. 4 shows the configuration of the first radio apparatus 10a. The first radio apparatus 10a includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, a baseband processing unit 22, a modem unit 24, an IF unit 26, a control unit 30, A timing synchronization unit 32 is included. Further, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, which is collectively referred to as a frequency domain signal 202, and a second time domain signal 200b. It includes a frequency domain signal 202b and a fourth frequency domain signal 202d. The second radio apparatus 10b is configured in the same manner as the first radio apparatus 10a.

  As a reception operation, the radio unit 20 performs frequency conversion on a radio frequency signal received by the antenna 12 and derives a baseband signal. The radio unit 20 outputs the baseband signal to the baseband processing unit 22 as a time domain signal 200. In general, baseband signals are formed by in-phase and quadrature components, so they should be transmitted by two signal lines. Here, only one signal line is used for the sake of clarity. Shall be shown. An AGC (Automatic Gain Control) and an A / D conversion unit are also included. The AGC sets a gain in “L-STF” and “HT-STF”.

  One of the packet signals received by the radio unit 20 is defined by the format shown in FIG. 3A (hereinafter referred to as “MIMO format”). That is, “HT-SIG” is placed after “L-STF”, “HT-STF” is placed after “HT-SIG”, and “Data 1” is placed after “HT-STF”. Has been placed. The packet signal is composed of a plurality of sequences, and the first sequence, that is, “HT-STF” arranged in another sequence with reference to “HT-STF” arranged in the reference sequence, is CDD. Has been made. Also, one of the packet receiving units received by the radio unit 20 is defined by the format shown in FIG. 3B (hereinafter referred to as “conventional format”). That is, “data” is arranged subsequent to “L-STF”.

  Here, the configuration up to “L-SIG” is common to the MIMO format and the conventional format. On the other hand, in the MIMO format, “HT-SIG” is arranged immediately after “L-SIG”, and in the conventional format, “data” is arranged immediately after “L-SIG”. Although details will be described later, the arrangement of signal points in “data” is different from the arrangement of signal points in “HT-SIG”.

  As a transmission operation, the radio unit 20 performs frequency conversion on the baseband signal from the baseband processing unit 22 and derives a radio frequency signal. Here, a baseband signal from the baseband processing unit 22 is also shown as a time domain signal 200. The radio unit 20 outputs a radio frequency signal to the antenna 12. Further, a PA (Power Amplifier) and a D / A converter are also included. The time domain signal 200 is a multicarrier signal converted into the time domain, and is a digital signal.

  When the received packet signal is in the MIMO format, the timing synchronization unit 32 detects timing in two stages. Here, for the sake of convenience, the timing detected in the first stage is referred to as a temporary timing, and the timing detected in the second stage is referred to as a timing as it is. Further, for the sake of clarity, the second stage process in the timing synchronization unit 32 will be described later. If the received packet signal is in a conventional format, only the first stage is executed. The timing synchronization unit 32 performs a correlation process on the L-STF in the packet signal from the radio unit 20, that is, the time domain signal 200, as a first stage process. Here, a cross-correlation process between the time domain signal 200 and the L-STF is executed as the correlation process. Note that the L-STF is stored in advance. Furthermore, the timing synchronization unit 32 detects the peak of the correlation value, and determines the timing corresponding to the detected peak of the correlation value as a temporary timing.

  Note that the timing synchronization unit 32 may execute the above processing on one of the plurality of time domain signals 200 or may execute the processing on each of the plurality of time domain signals 200. When processing is performed on one of the plurality of time domain signals 200, the one time domain signal 200 may be selected in a fixed manner, or may be selected based on signal strength or the like. In that case, the 1st radio | wireless apparatus 10a is equipped with the measurement part which is not shown in figure. Further, when processing is performed on each of the plurality of time domain signals 200, one temporary timing may be selected from the plurality of derived temporary timings, and the plurality of derived temporary timings may be selected. One tentative timing may be derived by performing statistical processing such as averaging on. The above processing is the same for the processing for the second stage. Here, for ease of explanation, here, it is assumed that correlation processing is performed on one time domain signal 200 that is fixedly selected. The timing synchronization unit 32 notifies the control unit 30 of the determined provisional timing.

  As a reception operation, the baseband processing unit 22 converts each of the plurality of time domain signals 200 into the frequency domain, and performs adaptive array signal processing on the frequency domain signal. The baseband processing unit 22 outputs the result of adaptive array signal processing as the frequency domain signal 202. One frequency domain signal 202 corresponds to each of a plurality of sequences transmitted from the second radio apparatus 10b (not shown). In the “L-LTF”, “L-SIG”, and “HT-SIG” periods in the MIMO format, and in the “L-LTF”, “L-SIG”, and “data” periods in the conventional format, The baseband processing unit 22 receives provisional timing from the control unit 30. The baseband processing unit 22 sets a window based on the received temporary timing and executes conversion to the frequency domain. Here, when the FFT is used for the conversion to the frequency domain, the window corresponds to an “FFT window”.

  On the other hand, the baseband processing unit 22 receives a timing, which will be described later, from the control unit 30 during a period of “HT-LTF”, “data 1”, etc. in the MIMO format. The baseband processing unit 22 sets a window based on the received timing and executes conversion to the frequency domain. Further, as a transmission operation, the baseband processing unit 22 receives a frequency domain signal 202 as a frequency domain signal from the modulation / demodulation unit 24, converts the frequency domain signal to the time domain, and transmits the frequency domain signal to each of the plurality of antennas 12. The time domain signal 200 is output while being associated.

  It is assumed that the number of antennas 12 to be used in the transmission process is specified by the control unit 30. Here, the frequency domain signal 202, which is a frequency domain signal, includes a plurality of subcarrier components as shown in FIG. For the sake of clarity, it is assumed that the frequency domain signals are arranged in the order of subcarrier numbers to form a serial signal.

  FIG. 5 shows the structure of a signal in the frequency domain. Here, one combination of subcarrier numbers “−28” to “28” shown in FIG. 1 is referred to as an “OFDM symbol”. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “28” and subcarrier numbers “−28” to “−1”. Also, the “i−1” th OFDM symbol is arranged before the “i” th OFDM symbol, and the “i + 1” th OFDM symbol is arranged after the “i” th OFDM symbol. And Note that, in the portions such as “L-SIG” in FIGS. 3A to 3B, combinations of subcarrier numbers “−26” to “26” are used for one “OFDM symbol”.

ここで、δは、シフト量を示し、ｌは、サブキャリア番号を示している。さらに、行列Ｃと系列との乗算は、サブキャリアを単位にして実行される。すなわち、ベースバンド処理部２２は、Ｌ−ＳＴＦ等内での循環的なタイムシフトを系列単位に実行する。また、シフト量は、図３（ａ）に対応するように、系列を単位にして異なった値に設定される。Returning to FIG. Further, the baseband processing unit 22 performs CDD in order to generate a packet signal corresponding to the packet format of FIG. CDD is performed as matrix C as follows.

Here, δ indicates a shift amount, and l indicates a subcarrier number. Further, the multiplication of the matrix C and the sequence is executed in units of subcarriers. That is, the baseband processing unit 22 performs a cyclic time shift within the L-STF or the like for each sequence. Further, the shift amount is set to a different value in units of series so as to correspond to FIG.

  The modem unit 24 performs demodulation and deinterleaving on the frequency domain signal 202 from the baseband processing unit 22 as reception processing. Note that demodulation is performed in units of subcarriers. The modem unit 24 outputs the demodulated signal to the IF unit 26. Further, the modem unit 24 performs interleaving and modulation as transmission processing. The modem unit 24 outputs the modulated signal to the baseband processing unit 22 as the frequency domain signal 202. It is assumed that the modulation scheme is specified by the control unit 30 during the transmission process.

  The modem unit 24 cooperates with the control unit 30 described later to demodulate “HT-SIG” in the frequency domain signal 202 converted at the tentative timing, so that “HT-STF” in the packet signal is demodulated. Detect presence. That is, in the packet signal demodulated by the modulation / demodulation unit 24, the control unit 30 corresponds to the arrangement of signal points in the latter part of “L-SIG” corresponding to the arrangement of signal points in “HT-SIG”. For example, the presence of “HT-SIG” is detected. In order to describe the above operation, the arrangement of signal points such as “HT-SIG” will be described.

  FIGS. 6A to 6B show constellations of L-SIG and HT-SIG. FIG. 6A shows a constellation defined for L-SIG. The horizontal axis represents the in-phase axis (hereinafter referred to as “I axis”), and the vertical axis represents the orthogonal axis (hereinafter referred to as “Q axis”). As shown in the figure, a signal point is arranged at “+1” or “−1” on the I axis. FIG. 6B shows a constellation defined for HT-SIG. As shown in the figure, signal points are arranged at “+1” or “−1” on the Q axis, and this arrangement is orthogonal to the signal point arrangement defined for L-SIG. Yes.

  That is, in the MIMO format, HT-SIG is arranged after L-SIG, but in the conventional format, HT-SIG is not arranged after L-SIG. For this reason, the control unit 30 specifies whether or not HT-SIG is arranged in the subsequent stage of L-SIG from the change in the demodulated BPSK constellation. In addition, in the data in the conventional format, QPSK and 16QAM may be used in addition to BPSK in FIG. 6 (a). However, unlike these in FIG. 6 (b), the signal point is the I axis. It has a predetermined value on the top. Therefore, by examining the value of the I axis of the demodulated signal, the control unit 30 can specify whether it is HT-SIG. Further, when HT-SIG is sent, the modulation scheme of the L-SIG portion is BPSK. If a packet signal corresponding to a conventional system is received, the modulation method of this part should be BPSK, and the value of the Q component is small. On the other hand, if HT-SIG is received, the value of the Q component increases. By such a device, the accuracy of Autodetection of HT-SIG is increased. Returning to FIG.

  The IF unit 26 combines signals from the plurality of modulation / demodulation units 24 as a reception process to form one data stream. Furthermore, one data stream is decoded. The IF unit 26 outputs the decoded data stream. In addition, the IF unit 26 receives and encodes one data stream as transmission processing, and then separates it. Further, the IF unit 26 outputs the separated data to the plurality of modulation / demodulation units 24. It is assumed that the coding rate is specified by the control unit 30 during the transmission process. Here, an example of encoding is convolutional encoding, and an example of decoding is Viterbi decoding.

  The control unit 30 controls the timing of the first radio apparatus 10a. When the control unit 30 receives the temporary timing from the timing synchronization unit 32, the control unit 30 notifies the baseband processing unit 22 and the modem unit 24 of the temporary timing. Further, as described above, the control unit 30 detects whether or not “HT-SIG” is present in the packet signal based on the signal demodulated by the modem unit 24. When the presence of “HT-SIG” is detected, the control unit 30 instructs the timing synchronization unit 32 to execute a correlation process for “HT-STF” in the time domain signal 200. When receiving the instruction, the timing synchronization unit 32 detects timing by executing a cross-correlation process between the time domain signal 200 from the radio unit 20 and the HT-STF. Details of timing detection will be described later.

  In the control unit 30, the window width when the timing synchronization unit 32 executes the cross-correlation process with “HT-STF” is the window width when the cross-correlation process with “L-STF” is executed. Instruct it to be narrower. When receiving the timing detected by the timing synchronization unit 32, the control unit 30 notifies the baseband processing unit 22 and the modem unit 24 of the timing. The baseband processing unit 22 and the modem unit 24 process “HT-LTF”, “Data 1”, etc. in the packet signal at the timing.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 7 shows a configuration of the timing synchronization unit 32. The timing synchronization unit 32 includes a correlation unit 34, a window setting unit 36, a peak detection unit 38, and a determination unit 40. The determining unit 40 includes a moving unit 42 and a comparing unit 44.

  The correlator 34 receives one time domain signal 200, cross-correlation processing (hereinafter referred to as “first stage”) between the time domain signal 200 and the L-STS, and the time domain signal 200 and the HT-LTF. The cross-correlation process (hereinafter referred to as “second stage”) is executed. The window width when executing the cross-correlation process is set by the window setting unit 36. The window setting unit 36 receives an instruction regarding the window width from the control unit 30 (not shown), and sets the window width of the correlation unit 34. As described above, the window setting unit 36 sets a window width that is somewhat long at the head portion of the packet signal, that is, at the first stage. In the second stage, the window setting unit 36 sets a shorter window width. As described above, the correlation process in the first stage and the correlation process in the second stage are executed in the correlation unit 34. That is, the correlators for the first stage and the second stage are shared. Therefore, an increase in circuit scale due to the correlator can be reduced. Note that the same pattern, that is, a waveform is used for the L-STF and the HT-STF.

  FIG. 8 shows the formats of L-STF and HT-STF. The L-STF is composed of ten patterns from the first pattern to the tenth pattern. One pattern is composed of 16 components. Note that the ten patterns are configured by the same pattern. That is, one pattern constituted by 16 components is repeated 10 times. On the other hand, in HT-STF, one pattern is repeated five times.

  FIG. 9 shows the configuration of the correlation unit 34. The correlator 34 includes a first delay unit 90a, an eighth delay unit 90h, a fifteenth delay unit 90o, and a first holding unit 92a, an eighth holding unit 92h, 16 holding part 92p, the 1st multiplication part 94a named generically as the multiplication part 94, the 8th multiplication part 94h, the 16th multiplication part 94p, and the addition part 96 are included.

  As shown in the drawing, the correlation unit 34 has a matched filter configuration and generates a correlation value. The delay unit 90 sequentially delays the input time domain signal 200. The holding unit 92 stores an L-STF pattern, that is, a waveform. Here, the 16 components included in one pattern are stored in the first holding unit 92a to the sixteenth holding unit 92p, respectively. The multiplication unit 94 performs multiplication between the input time domain signal 200, the time domain signal 200 from the delay unit 90, and the pattern stored in the holding unit 92. The addition unit 96 sequentially generates correlation values by adding the multiplication results from the multiplication unit 94.

  Here, in the first stage, the addition unit 96 adds the multiplication results from the multiplication result in the first multiplication unit 94a to the sixteenth multiplication unit 94p. That is, the adding unit 96 adds 16 multiplication results. For this reason, the “somewhat long window width” is defined as the number of components included in one pattern. On the other hand, in the second stage, the adder 96 adds the multiplication results from the first multiplier 94a to the eighth multiplier 94h. That is, the adding unit 96 adds eight multiplication results. Here, the window width of the eight components corresponds to the absolute value “400 nsec” of the shift amount in FIG. When the absolute value “200 nsec” of the shift amount in FIG. 3A is taken into account, the adding unit 96 may add four multiplication results. Therefore, the aforementioned “shorter window width” is defined as a number that is smaller than the number of components included in one pattern and that can separate the delayed wave components generated by CDD.

  FIGS. 10A and 10B show delay profiles of signals input to the correlation unit 34. FIG. Here, the packet signal is assumed to be composed of two sequences. FIG. 10A shows a delay profile in the first stage. The horizontal axis indicates the delay time, and the vertical axis indicates the signal intensity. Note that the delay time of the preceding wave is “0 ns”. In FIG. 10A, the L-STF in the first sequence and the L-STF in the second sequence are synthesized as they are, so that the signal strength increases when the delay time is in the vicinity of 0 to 50 nsec. . Therefore, when the delay time is in the vicinity of 0 to 50 nsec, the correlation value derived by the correlation unit 34 is the largest. However, depending on the transmission path characteristics, these L-STFs may be combined so as to cancel each other. In this case, since the signal strength is reduced when the delay time is 0 to 50 nsec, the influence of the signal strength after the delay time of 50 nsec becomes relatively large. Therefore, when the delay time becomes longer than 50 nsec, the correlation value derived by the correlation unit 34 becomes the largest. In order to deal with this, as described above, the window width is defined to be the length of one pattern in the first stage.

  FIG. 10B shows a delay profile in the second stage. In FIG. 10A, since the L-STF in the first sequence and the L-STF in the second sequence are combined as they are, the signal strength increases in the vicinity of the delay times of 0 nsec and 400 nsec. When the window width at the first stage is set for a signal having such a delay profile, the correlation value becomes the largest at a timing between 0 nsec and 400 nsec. That is, the two peaks of the delay profile cannot be separated. Therefore, in the second stage, the window width is defined to be half the length of one pattern. Returning to FIG.

  The peak detector 38 detects the peak of the correlation value from the correlator 34. In the first stage, the peak detector 38 detects one peak. The peak detection unit 38 sets a threshold value in advance, and detects the presence of the L-STF when the value of the peak correlation value exceeds the threshold value. When detecting the presence of the L-STF, the peak detection unit 38 notifies the determination unit 40 of the timing at that time. If the correlation value of the peak does not exceed the threshold value, the peak detector 38 continues to detect the peak.

  On the other hand, the peak detector 38 detects peaks corresponding to delay times of 0 nsec, −400 nsec, −200 nsec, and −600 nsec in the second stage. These correspond to the time shift amount in CDD applied to the HT-STF. That is, based on the correlation value, the peak detection unit 38 determines the timing corresponding to the first sequence HT-STF and the timing corresponding to the second sequence to the fourth sequence HT-STF. Detect as a candidate. The peak detection unit 38 performs detection in the order of delay times 0 nsec, −400 nsec, −200 nsec, and −600 nsec. That is, the peak detector 38 detects a peak near the delay time of −600 nsec when it detects a peak near the delay time of −200 nsec, but does not detect a peak near the delay time of −600 nsec when it does not detect it. In this case, the number of the plurality of series is specified as “2”. The peak detection unit 38 notifies the determination unit 40 of the detected timing candidates.

  When receiving the timing from the peak detection unit 38 in the first stage, the determination unit 40 notifies the control unit 30 (not shown) of the timing as a temporary timing. On the other hand, the determination unit 40 receives timing candidates from the peak detection unit 38 in the second stage. The determination unit 40 selects a timing from the timing candidates while using the moving unit 42 and the comparison unit 44, and notifies the control unit 30 (not shown) of the selected timing.

  The moving unit 42 moves the timing for each of the timing candidates. Note that the moving unit 42 moves the timing according to the timing shift amount with respect to the timing corresponding to the HT-STF to which the timing shift has been performed among the timing candidates. For example, the moving unit 42 selects a timing corresponding to the delay amount −400 nsec from the timing candidates, and moves the selected timing backward by 400 nsec. The moving unit 42 selects a timing corresponding to the delay amount −200 nsec from the timing candidates, and moves the selected timing backward by 200 nsec. Further, the moving unit 42 performs the same process for the timing corresponding to the delay amount of 600 nsec. Through the above processing, the moving unit 42 makes a state in which the timing corresponding to the HT-STF subjected to the timing shift and the timing corresponding to the first sequence can be compared.

  The comparing unit 44 determines the timing based on the timing moved by the moving unit 42 and the timing corresponding to the first series. Here, the timing existing ahead is selected from the timing moved by the moving unit 42 and the timing corresponding to the first sequence. When a backward timing is selected, there is a possibility that one OFDM symbol specified at the timing is the next OFDM symbol and overlaps with an actual OFDM symbol. At this time, interference between OFDM symbols occurs, and reception characteristics are likely to deteriorate. In order to suppress such deterioration, the comparison unit 44 selects the timing that exists most forward.

  FIGS. 11A to 11D show an outline of timing determination in the determination unit 40. FIG. Here, for the sake of clarity of explanation, a case where a timing corresponding to the first sequence of HT-STF and a timing corresponding to the second sequence of HT-STF are detected as timing candidates will be described. To do. In addition, the horizontal axis of the figure indicates time, and the arrow indicates timing. FIG. 11A shows two timing candidates detected by the peak detector 38. Here, “A” corresponds to the timing corresponding to the HT-STF of the second sequence, and “B” corresponds to the timing corresponding to the HT-STF of the first sequence. “B” is detected at a timing of 450 nsec.

  FIG. 11B shows a case where “A” in FIG. 11A is moved backward by 400 nsec by the moving unit 42. By such movement, “A” is located at a timing of 400 nsec. The comparison unit 44 compares “A” positioned at a timing of 400 nsec with “B” positioned at a timing of 450 nsec, and selects a timing existing ahead. Here, “A” is selected. Furthermore, the determination unit 40 notifies the control unit 30 (not shown) of the selected timing.

  FIG. 11C shows two timing candidates detected by the peak detector 38, as in FIG. 11A. However, in FIG. 11C, “B” is detected at a timing of 350 nsec. FIG. 11D shows a case where “A” in FIG. 11C is moved backward by 400 nsec by the moving unit 42. By such movement, “A” is located at a timing of 400 nsec. The comparison unit 44 selects the timing “B” present ahead by comparing “A” positioned at the timing of 400 nsec with “B” positioned at the timing of 350 nsec. Furthermore, the determination unit 40 notifies the control unit 30 (not shown) of the selected timing. Here, for the sake of clarity, “A” is present at the timing of 0 nsec, but may actually exist at other timings.

  FIG. 12 shows the configuration of the baseband processing unit 22. The baseband processing unit 22 includes a reception processing unit 50 and a transmission processing unit 52. The reception processing unit 50 executes a part corresponding to the reception operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 performs adaptive array signal processing on the time domain signal 200, and for that purpose, derivation of the weight vector of the time domain signal 200 is performed. Further, the reception processing unit 50 outputs the result of array synthesis as the frequency domain signal 202.

  The transmission processing unit 52 executes a part corresponding to the transmission operation among the operations in the baseband processing unit 22. That is, the transmission processing unit 52 generates the time domain signal 200 by converting the frequency domain signal 202. In addition, the transmission processing unit 52 associates a plurality of sequences with the plurality of antennas 12, respectively. Further, the transmission processing unit 52 executes CDD as shown in FIG. Note that the transmission processing unit 52 finally outputs the time domain signal 200.

  FIG. 13 shows a configuration of the reception processing unit 50. The reception processing unit 50 includes an FFT unit 74, a weight vector deriving unit 76, a first combining unit 80a, a second combining unit 80b, a third combining unit 80c, and a fourth combining unit 80d, which are collectively referred to as a combining unit 80.

  The FFT unit 74 converts the time domain signal 200 into a frequency domain value by performing FFT on the time domain signal 200. Here, it is assumed that the frequency domain values are configured as shown in FIG. That is, the frequency domain value for one time domain signal 200 is output on one signal line. Note that the FFT unit 74 performs FFT based on the FFT window set at the tentative timing over “L-LTF”, “L-SIG”, and “HT-SIG” in FIG. To do. On the other hand, over the “HT-LTF”, “Data 1”, etc. of FIG. 3A, the FFT unit 74 executes the FFT based on the FFT window set at the timing. Also, the FFT unit 74 performs FFT based on the FFT window set at the tentative timing over “L-LTF”, “L-SIG”, and “data” in FIG.

  The weight vector deriving unit 76 derives a weight vector for each subcarrier from the value in the frequency domain. The weight vector is derived so as to correspond to each of a plurality of sequences, and the weight vector for one sequence has an element corresponding to the number of antennas 12 for each subcarrier. Further, HT-LTF or the like is used for deriving the weight vector corresponding to each of the plurality of sequences. In order to derive the weight vector, an adaptive algorithm may be used, or transmission path characteristics may be used. However, since a known technique may be used for these processes, here, The description is omitted. Note that the weight vector deriving unit 76 calculates the first component−the second component + the third component−the fourth component as described above when deriving the weight. Finally, as described above, weights are derived in units of subcarriers, antennas 12 and sequences.

  The synthesizing unit 80 performs synthesis using the frequency domain value converted by the FFT unit 74 and the weight vector from the weight vector deriving unit 76. For example, among the weight vectors from the weight vector deriving unit 76, a weight vector corresponding to one subcarrier and corresponding to the first series is selected as one multiplication target. The selected weight has a value corresponding to each of the antennas 12.

  As another multiplication target, a value corresponding to one subcarrier is selected from the values in the frequency domain converted by the FFT unit 74. The selected value has a value corresponding to each of the antennas 12. Note that the selected weight and the selected value correspond to the same subcarrier. While being associated with each of the antennas 12, the selected weight and the selected value are respectively multiplied, and the multiplication result is added, whereby a value corresponding to one subcarrier in the first sequence is obtained. Derived. In the first synthesizing unit 80a, the above processing is also performed on other subcarriers, and data corresponding to the first stream is derived. Further, in the second synthesis unit 80b to the fourth synthesis unit 80d, data corresponding to the fourth series is derived from the second series by the same processing. The derived first to fourth sequences are output as the first frequency domain signal 202a to the fourth frequency domain signal 202d, respectively.

  FIG. 14 shows the configuration of the transmission processing unit 52. The transmission processing unit 52 includes a distribution unit 66 and an IFFT unit 68. Note that an IFFT unit 68 may be disposed downstream of the dispersion unit 66. The IFFT unit 68 performs IFFT on the frequency domain signal 202 and outputs a time domain signal. As a result, the IFFT unit 68 outputs a time domain signal corresponding to each of the sequences.

  The distribution unit 66 associates the series from the IFFT unit 68 with the antenna 12. Here, since the number of antennas 12 used and the number of series are the same, one series is associated with one antenna 12 as it is. Furthermore, the distribution unit 66 performs CDD on “L-SIG” or the like in each of the sequences to be transmitted, that is, packet signals.

  The operation of the wireless device 10 having the above configuration will be described. FIG. 15 is a flowchart illustrating a procedure of timing synchronization processing in the timing synchronization unit 32. The window setting unit 36 sets the window width of the correlation unit 34 to “16” based on an instruction from the control unit 30 (S10). If the peak detection unit 38 detects “L-STF” as a result of the correlation processing performed by the correlation unit 34 under such a window width (Y in S12), the determination unit 40 detects the provisional timing. (S14). On the other hand, if the peak detection unit 38 does not detect “L-STF” (N in S12), the correlation processing is repeatedly executed.

  If the control unit 30 detects “HT-SIG” as a result of demodulation by the modem unit 24 (Y in S16), the window setting unit 36 determines the window width of the correlation unit 34 based on an instruction from the control unit 30. Is set to “8” (S18). As a result of the correlation processing performed by the correlation unit 34 under such a window width, the peak detection unit 38 and the determination unit 40 detect timing (S20). Based on the detected timing, the baseband processing unit 22 and the modem unit 24 process the data (S22). On the other hand, if the control unit 30 does not detect “HT-SIG” (N in S16), the baseband processing unit 22 and the modem unit 24 process the data based on the detected provisional timing (S24). .

  According to the embodiment of the present invention, the width of the window when executing the correlation process in the second stage is set to be narrower than the width of the window when executing the correlation process in the first stage. The L-STF can be detected with high probability in the first stage, and the timing can be detected with high accuracy in the second stage. In addition, since the window width when executing correlation processing in the first stage is widened, even if the sequences arriving at the head portion cancel each other due to the influence of the transmission path characteristics, the sequences arriving at the rear portion are detected. it can. In addition, since a sequence arriving at the rear portion can be detected, L-STF can be detected with high probability. In addition, since the L-STF is detected with a high probability, the signal following the L-STF can be reliably processed.

  In addition, since the window width when executing the correlation process in the second stage is narrowed, a plurality of sequences constituting the received packet signal can be separated. Since a plurality of sequences are separated, the timing corresponding to each of the plurality of sequences can be detected. Moreover, since the correlator which should be used for two correlation processes is shared in the 1st stage and the 2nd stage, the increase in a circuit scale can be reduced. In addition, since cross-correlation is used as the two correlation processes, the influence of noise can be reduced, and the detection accuracy of the correlation value peak can be improved. Further, since the detection accuracy of the correlation value peak can be improved, provisional timing and timing detection accuracy can be improved. Further, since the presence of HT-SIG is detected according to the arrangement of signal points, it can be automatically detected. Moreover, since it can detect automatically, the additional signal for notifying presence can be made unnecessary and the deterioration of transmission efficiency can be prevented.

  Further, by detecting the presence of HT-SIG, it is possible to specify whether the packet signal is in the MIMO format or the conventional format. In addition, since one timing is determined from the timing corresponding to each of the plurality of sequences, the influence of each of the plurality of sequences can be taken into account, and the timing can be detected with high accuracy. Moreover, since the timing existing ahead is selected from a plurality of timings, interference with the OFDM symbol arranged behind can be reduced, and reception characteristics can be improved.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the correlation unit 34 executes the cross-correlation process for both the first stage and the second stage. However, the present invention is not limited to this. For example, the correlation unit 34 may execute the autocorrelation process in the first stage and the cross-correlation process in the second stage. In this case, the holding unit 92 may store the time domain signal 200 that has already been received. Also in such a configuration, the window setting unit 36 sets the window width in the second stage to be narrower than the window width in the first stage. In addition, the correlation unit 34 may perform autocorrelation processing in both the first stage and the second stage. According to this modification, the detection probability of L-STF in the first stage can be improved. That is, in the second stage, the correlation process may be executed with a window width narrower than that in the first stage.

  In the embodiment of the present invention, after the timing is detected by the timing synchronization unit 32, the baseband processing unit 22 and the modem unit 24 receive “HT-LTF”, “Data 1”, etc. based on the timing. Processing. However, the present invention is not limited to this. For example, after the timing is detected, the baseband processing unit 22 and the modem unit 24 may receive and process “L-STF”, “L-SIG”, and “HT-SIG”. Therefore, the wireless device 10 is provided with a storage unit for storing the time domain signal 200, and after the timing is detected, the baseband processing unit 22 and the modem unit 24 are included in the time domain signal 200 stored in the storage unit. "L-STF", "L-SIG", and "HT-SIG" are processed again. According to this modification, “HT-SIG” is received again at the timing detected with high accuracy, so that the processing accuracy of “HT-SIG” can be improved.

  In the Example of this invention, the comparison part 44 has selected the timing which exists most forward among several timings. However, the present invention is not limited to this. For example, the comparison unit 44 may determine the timing by executing statistical processing on a plurality of timings. For example, the averaging process may be performed on the timing while performing weighting according to the correlation value corresponding to each timing. According to this modification, the timing can be determined while considering the influence of a plurality of timings.

  According to the present invention, the timing can be detected while taking into account the delayed wave component.

Claims (8)

The first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data signal is arranged after the second known signal. A receiving unit for receiving the received packet signal;
First detection for detecting a provisional timing while detecting the presence of the first known signal in the packet signal by performing correlation processing on the first known signal among the packet signals received by the receiving unit And
A first processing unit for detecting the presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit;
When the presence of the second known signal is detected by the first processing unit, a timing is detected by executing a correlation process on the second known signal among the packet signals received by the receiving unit. A detection unit;
A second processing unit that processes a second data signal in the packet signal at a timing detected by the second detection unit;
The width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit ,
The packet signal received by the receiving unit is composed of a plurality of sequences, and a second known signal arranged in another sequence on the basis of a second known signal arranged in one of the plurality of sequences. The signal has a cyclic timing shift within the second known signal,
The second detector is
A deriving unit for deriving, as timing candidates, a timing corresponding to the second known signal serving as a reference based on the correlation value and a timing corresponding to the second known signal subjected to timing shift;
Among the timing candidates derived by the deriving unit, a moving unit that performs a timing shift according to the timing shift amount with respect to the timing corresponding to the second known signal that has been subjected to the timing shift;
A determination unit that determines the timing based on the timing moved by the moving unit and the timing corresponding to the second known signal serving as a reference among the timing candidates derived in the deriving unit; A receiving device. The first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data signal is arranged after the second known signal. A receiving unit for receiving the received packet signal;
First detection for detecting a provisional timing while detecting the presence of the first known signal in the packet signal by performing correlation processing on the first known signal among the packet signals received by the receiving unit And
A first processing unit for detecting the presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit;
When the presence of the second known signal is detected by the first processing unit, a timing is detected by executing a correlation process on the second known signal among the packet signals received by the receiving unit. A detection unit;
A second processing unit that processes a second data signal in the packet signal at a timing detected by the second detection unit;
The first known signal and the second known signal of the packet signals received by the receiving unit include the same pattern ,
The packet signal received by the receiving unit is composed of a plurality of sequences, and a second known signal arranged in another sequence on the basis of a second known signal arranged in one of the plurality of sequences. The signal has a cyclic timing shift within the second known signal,
The second detector is
A deriving unit for deriving, as timing candidates, a timing corresponding to the second known signal serving as a reference based on the correlation value and a timing corresponding to the second known signal subjected to timing shift;
Among the timing candidates derived by the deriving unit, a moving unit that performs a timing shift according to the timing shift amount with respect to the timing corresponding to the second known signal that has been subjected to the timing shift;
A determination unit that determines the timing based on the timing moved by the moving unit and the timing corresponding to the second known signal serving as a reference among the timing candidates derived in the deriving unit; A receiving device. The first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data signal is arranged after the second known signal. A receiving unit for receiving the received packet signal;
A first detection unit that detects provisional timing while detecting the presence of the first known signal in the packet signal by executing correlation processing between the packet signal received by the reception unit and the first known signal When,
A first processing unit for detecting the presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit;
Second detection for detecting timing by executing correlation processing between the packet signal received by the receiving unit and the second known signal when the presence of the second known signal is detected by the first processing unit And
A second processing unit that processes a second data signal in the packet signal at a timing detected by the second detection unit;
The width of the window when executing the correlation process in the second detection unit is set to be narrower than the width of the window when executing the correlation process in the first detection unit ,
The packet signal received by the receiving unit is composed of a plurality of sequences, and a second known signal arranged in another sequence on the basis of a second known signal arranged in one of the plurality of sequences. The signal has a cyclic timing shift within the second known signal,
The second detector is
A deriving unit for deriving, as timing candidates, a timing corresponding to the second known signal serving as a reference based on the correlation value and a timing corresponding to the second known signal subjected to timing shift;
Among the timing candidates derived by the deriving unit, a moving unit that performs a timing shift according to the timing shift amount with respect to the timing corresponding to the second known signal that has been subjected to the timing shift;
A determination unit that determines the timing based on the timing moved by the moving unit and the timing corresponding to the second known signal serving as a reference among the timing candidates derived in the deriving unit; A receiving device.   4. The correlator for executing correlation processing in the first detection unit and the correlator for executing correlation processing in the second detection unit are shared. The receiving device described. The first data signal is arranged after the first known signal, the second known signal is arranged after the first data signal, and the second data signal is arranged after the second known signal. A receiving unit for receiving the received packet signal;
A first detection unit that detects provisional timing while detecting the presence of the first known signal in the packet signal by performing autocorrelation processing on the packet signal received by the reception unit;
A first processing unit for detecting the presence of a second known signal in the packet signal by processing the first data signal in the packet signal at the tentative timing detected by the first detection unit;
When the presence of the second known signal is detected by the first processing unit, a timing is detected by executing a cross-correlation process between the packet signal received by the receiving unit and the second known signal. A detection unit;
A second processing unit that processes a second data signal in the packet signal at a timing detected by the second detection unit;
The width of the window when executing the cross-correlation process in the second detection unit is set to be narrower than the width of the window when executing the autocorrelation process in the first detection unit ,
The packet signal received by the receiving unit is composed of a plurality of sequences, and a second known signal arranged in another sequence on the basis of a second known signal arranged in one of the plurality of sequences. The signal has a cyclic timing shift within the second known signal,
The second detector is
A deriving unit for deriving, as timing candidates, a timing corresponding to the second known signal serving as a reference based on the correlation value and a timing corresponding to the second known signal subjected to timing shift;
Among the timing candidates derived by the deriving unit, a moving unit that performs a timing shift according to the timing shift amount with respect to the timing corresponding to the second known signal that has been subjected to the timing shift;
A determination unit that determines the timing based on the timing moved by the moving unit and the timing corresponding to the second known signal serving as a reference among the timing candidates derived in the deriving unit; A receiving device. The receiving unit also receives another packet signal including the first known signal, and in the other packet signal, the arrangement of signal points in the subsequent stage of the first known signal is the first Different from the arrangement of signal points in at least part of the data signal,
In the first processing unit, among the packet signals received by the receiving unit, the signal point arrangement in the subsequent stage of the first known signal is changed to the signal point arrangement in at least a part of the first data signal. 6. The receiving apparatus according to claim 1, wherein if it is compatible, the presence of the second known signal in the packet signal is detected. The determination unit selects a timing that exists ahead of the timing moved by the moving unit and the timing corresponding to the second known signal that is a reference among the timing candidates derived by the deriving unit. The receiving apparatus according to claim 1, wherein the receiving apparatus is a receiver. A storage unit for storing the packet signal received by the reception unit;
When the second processing unit processes the second data signal in the packet signal at the timing detected by the second detection unit, the first data signal in the packet signal stored in the storage unit is again processed. the receiving apparatus according to claim 1, characterized in that the process 7.

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